Faraday Method Research Articles

A preliminary investigation into the feasibility of laser ablation U-Pb isotope ratio measurement via all-faraday cup detection with 1011- and 1013-Ω amplifiers on the Neoma multicollector-inductively coupled plasma-mass spectrometer.

Signal detection for uranium-lead (U-Pb) dating of zircon is typically performed via ion counters. Here, we develop a preliminary understanding of the strengths and limitations of faraday-cup-based detection. A suite of zircon reference materials and the NIST-610 glass were sampled using laser ablation followed by U-Pb isotope ratio measurement on a Neoma multicollector-inductively coupled plasma-mass spectrometer. We were able to produce geologically accurate 207Pb/206Pb, 206Pb/238U, and 207Pb/235U ratios for the NIST-610 glass and the zircon standards, with ages ranging from ~2.5Ga to ~337 Ma (TanBrown A, Oracle, 91550, Mud Tank, Temora, and Plešovice). Two of the younger zircon standards examined (94-35, ~55.6Ma, and Fish Canyon, 28.6Ma) yielded accurate 206Pb/238U but not 207Pb/235U or 207Pb/206Pb ratios, whereas the youngest zircon standard (Penglai, ~4.4Ma) failed for all three ratios of interest. The accuracy and precision of the all-faraday method are directly tied to signal intensity, with reliable data capable of being produced even when both isotopes in a ratio have signals below ~0.001 V (equivalent to ~62 500 cps on an ion counter). The all-faraday cup multicollection method provides sufficient sensitivity to obtain geologically meaningful U-Pb data, with possible advantages being that laser pit depth-dependent changes in the observed interelemental fractionation behavior may be easier to correct using a static collector configuration compared to when the ion beam is swept across a single detector while also removing the need for an interdetector-type calibration. Further work is needed to refine the all-faraday cup method (e.g., application of background subtraction and common Pb corrections, outlier removal, and interelement as well as down-hole fractionation corrections), but our initial results demonstrate that the faraday detector method has sufficient sensitivity to warrant further study.

Impact of GO on Non-stoichiometric Mg0.85 K0.3Fe2O4 Ferrite Nanoparticles

Graphene oxide (GO) nanostructures are systems with many fascinating novel properties that can be used to study new science and have significant promise for applications. In this study, graphene oxide was prepared using the modified Hummer’s method. In addition, potassium ferrite is a good candidate for biomedical application, as iron and potassium are biocompatible and non-toxic materials. Mg0.85K0.3Fe2O4/GO nanocomposites were prepared by the citrate auto-combustion method. The effect of adding GO to Mg0.85K0.3Fe2O4 on structure, morphology, electrical, and magnetic properties was discussed. Samples under investigation were characterized using XRD, infrared spectroscopy (IR), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The crystallite size of prepared samples was decreased from 28.098 to18.148 nm by increasing GO content. Scanning electron microscope (SEM) confirms the successful adhesion of Mg0.85K0.3Fe2O4 nanoparticles on graphene oxide sheets, which are dispersed in a metal oxide matrix. EDAX analysis confirms the existence of C, O, K, Mg, and Fe elements present in the samples. Magnetic properties were studied by VSM and Faraday's method. GO has a significant effect on the magnetic properties of nanocomposites. For instance, the saturation magnetization and Curie temperature have diverse values, which will be appropriate for numerous applications.

Radar-absorbing composite materials based on ferrite powders

The paper studies the effect of particle sizes of hexagonal ferrite powders on their electrodynamic properties. SrTi0.2Co0.2Fe11.6O19 and BaSc0.2Fe11.8O19 hexaferrites were used as the objects of research. Grinding in a high-energy planetary mill for up to 60 minutes made it possible to obtain hexaferrite powder particles with the average size successively decreasing from 1.5–2 μm to 0.05–0.15 μm. A scanning electron microscope was used for the analysis. Samples were prepared in a mixture with a polymer binder (70% ferrite + 30% polymer), and their electromagnetic radiation (EMR) absorbing capacity was studied in the microwave range from 30 to 50 GHz. It was shown that there is practically no peak corresponding to ferrimagnetic resonance in the composite with ferrite, with a decrease in the average particle size of BaSc0.2Fe11.8O19 hexaferrite powders to 50–150 nm. The dependences of the real and imaginary parts of the magnetic permeability and dielectric constant are given in the frequency range from 107 to 109 Hz. There was no domain wall resonance in the frequency dependence of magnetic losses for a ferrite-based composite mechanically activated for 60 min. SrTi0.2Co0.2Fe11.6O19 ferrite was milled in a bead mill to particles with an average size of 150–300 nm, and then to drying, pressing, sintering at 1360 °С and subsequent grinding to a size of 200–500 μm to obtain similar composites in a bond with a polymer. It was found that the properties of compositions change significantly with a change in the magnetic component synthesis technology: no resonant pattern of EMR absorption was observed. The Curie temperature was measured using the Faraday method. It was shown that it is ~340 °С for the studied material. Therefore, the effect of precursor milling on changes in magnetocrystalline anisotropy was identified.

STUDIES OF THERMOMETRIC MATERIAL Lu1-xZrxNiSb

The results of experimental research of perspective thermometric material Lu1-xZrxNiSbwhich can be used for the production of sensitive elements of thermoelectric and electroresistive thermometers are presented. Thermometric materials Lu1-xZrxNiSb, x=0.01–0.10, were made by fusing a charge of components in an electric arc furnace with a tungsten electrode (cathode) in an atmosphere of purified argon under a pressure of 0.1 kPa on a copper water-cooled hearth (anode). Heat treatment of alloys consisted of homogenizing annealing at a temperature of 1073 K. Annealing of samples was carried out for 720 h in vacuumed up to 1.0 Pa ampoules of quartz glass in muffle electric furnaces with temperature control with an accuracy of ±10 K. Diffraction arrays were obtained on a diffractometer DRON-4.0 (FeKα radiation), and the structural characteristics of Lu1-xZrxNiSbwere calculated using the Fullprof program. The chemical and phase compositions of the samples were monitored using a scanning electron microscope (Tescan Vega 3 LMU). The study of the temperature dependences of the resistivity ρ(T,x) and the thermopower coefficientα(T,x) Lu1-xZrxNiSb was performed in the temperature range of 80÷400 K on samples in the form of rectangular parallelepipeds measuring ~1.0×1.0×5.0 mm3 . Measurements of the values of the specific magnetic susceptibility χ(x) of Lu1-xZrxNiSb samples were performed by the relative Faraday method at a temperature of 273 K using a thermogravimetric installation with an electronic microbalance EM-5-ZMP in magnetic fields up to 10 kGs. Microprobe analysis of the concentration of atoms on the surface of Lu1-xZrxNiSb samples, x=0.01–0.10, established their correspondence to the initial compositions of the charge, and X-ray phase analysis showed no traces of extraneous phases on the sample diffractograms, except for the main phase. The nonmonotonic nature of the change in the values of the unit cell period of the thermometric material an (x) Lu1-xZrxNiSb, x=0.01–0.10, which differs from the results of modeling structural characteristics using software packages AkaiKKR and Elk. The nonmonotonic change in the values of the period of the unit cell a(x) Lu1-xZrxNiSband the presence of the extremum dependence suggests that the impurity Zr atoms introduced into the matrix of the LuNiSb basic semiconductor can simultaneously occupy partially different crystallographic positions in different ratios. The temperature resistivities ρ and the thermopower coefficientα of the LuNiSb base semiconductor contain high- and lowtemperature activation regions, which is characteristic of doped and compensated semiconductors. The introduction into the LuNiSb structure of the lowest concentration of impurity Zr atoms in the experiment (x=0.01) radically changes both the behavior of the temperature dependences of the resistivity ρ and the thermopower coefficientα and the type of the main electric current carriers. The values of the resistivity ρ(T,x) Lu1-xZrxNiSbonly increase with increasing temperature, which is characteristic of the metallic type of electrical conductivity and is due to the mechanisms of scattering of current carriers. This nature of the change in electrical resistance ρ(T,x) is evidence that the Fermi level εF has left the bandgap εg and is in the conduction band εC. This is indicated by the negative values of thermopower coefficientα(T,x) at all concentrations and temperatures. Studies of the magnetic susceptibility χ(x) showed that the samples as a basic semiconductor LuNiSb, as well as the thermometric material Lu1-xZrxNiSb, at all concentrations of impurities Zr, are Pauli paramagnetic. There is a synchronicity of the behavior of χ(x) with the dependences of the resistivity ρ(x, T) and the thermopower coefficient α(x, T), which is due to the change in the density of states at the Fermi level g(εF). The results of experimental studies of the Lu1-xZrxNiSbthermometric material completely coincide with the results of modeling its kinetic characteristics under the presence of vacancies in the crystallographic positions 4a and 4c of the Lu and Ni atoms, respectively. Such studies allow making adjustments in the structural studies of thermometric material with an accuracy that significantly exceeds the accuracy of X-ray research methods. The obtained results will allow us to clarify the spatial arrangement of atoms in the nodes of the unit cell, as well as to identify the mechanisms of electrical conductivity to determine the conditions for the synthesis of thermosensitive materials with maximum efficiency of thermal energy conversion into electricity.

INVESTIGATION OF SENSITIVE ELEMENTS OF TEMPERATURE TRANSDUCERS BASED ON THERMOMETRIC MATERIAL Lu1-xScxNiSb

INVESTIGATION OF SENSITIVE ELEMENTS OF TEMPERATURE TRANSDUCERS BASED ON THERMOMETRIC MATERIAL Lu1-xScxNiSb

Electrochemical studies of iron(II) complexeswith 4‐amino‐1,2,4‐triazole possessing spin crossover

AbstractThe electrochemical properties of a number of coordination compounds of iron(II) with 4‐amino‐1,2,4‐triazole (NH2trz), which have a sharp thermally induced spin crossover with hysteresis on the temperature curves of the effective magnetic moment dependence, were studied using method cyclic voltammetry (CV) at 298 K. The complexes were mixed with carbon powder and silicon oil and included in the paste electrode. The measurements were made in solutions of 0.10 M KNO3. It was found that the area 0.5–0.6 V and 0.3–0.4 V contains the anode and cathode current peaks of freshly prepared paste electrodes. In all cases, the redox process in the paste is quasi‐reversible. At the same molar concentration of complexes in the paste (0.1 mol kg−1), a number of current peaks depends on the nature of the anion. The peak current value correlates with the calculated fraction of the high spin form in the solid phase of the complex and the temperature of the direct spin crossover (when heated, Tc↑). The magnetic properties of Fe(NH2trz)3(NO3)2 complex, its mixture with carbon powder and the paste were measured by Faraday method in a temperature range 80–370 K. The effective magnetic moment was depended on changes in variations in the environment of the molecules of the complex in the studied samples.

Hybrid magnetic materials based on polyethylene containing Co and Ni nanoparticles

New hybrid magnetic materials based on HDPE filled with Со and Ni nanoparticles have been prepared via the metal vapor synthesis. Properties of the metal-polymer composites have been elucidated as a function of MVS parameters and metal nature. The Faraday method has been applied to characterize the magnetic properties of the systems. The microstructure of the samples has been studied with a number of X-ray and synchrotron techniques, including XRD, EXAFS and SAXS. Core-level and valence band spectra were measured by XPS. The peak at binding energy of 282.8 eV characteristic of C-Ni bond was recorded in the C 1s spectrum. It was shown that properties of nanocomposite materials with similar compositions are determined both by the synthesis conditions and post-synthesis factors.

The cobalt and nickel-containing polyethylene prepared by using metal-vapor synthesis

Cobalt and nickel-containing low-pressure polyethylene samples (HDPE) were prepared by metal-vapor synthesis (MVS) of unstable bisarene complexes of Ni and Co type (C6H5CH3)2M and their further decomposition at a temperature of 178 K in the volume of HDPE. The Faraday method shows that Ni and Co nanometer particles are stabilized by the polyethylene matrix up to T=370 K. When the Ni-HDPE material is heated above 420 K, irreversible processes of interaction of Ni clusters with the polyethylene matrix occur with the formation of a less magnetic phase. When the Co-HDPE material is heated above 420 K, Co clusters coalesce to form a more magnetic phase. At temperatures above 520 K, the magnetization of the Co/HDPE system begins to increase rapidly and approaches the value characteristic of massive cobalt. Changing the conditions of cryosynthesis significantly influences the properties of the resulting products. The sample of 2.5% Co-HDPE obtained at a temperature of 185 K is characterized by weak magnetic properties. Its magnetization at room temperature is lower than that of the samples with a similar metal content by 30-40 times. The XPS shows that nickel atoms are in the form of Ni(OH)2.

X-ray diffraction and magnetic properties of vanadium dioxide VO2±X solid solutions V1-XFeXO2

The article considers the results of vanadium dioxide VO2±X study (within the homogeneity range) and solid solutions V1-XFeXO2, obtained by X-ray diffraction and the Faraday method. The temperature dependences of the magnetic susceptibility samples are presented, and it follows that dependence χ (T) character in the temperature range from 100 К up to 250 К is close to Curie law for paramagnetic in the area of the phase transition at temperature Tmp ∼ 340 К, and there is an abrupt change in χ. It is considered that the magnetic properties of vanadium dioxide vary both with the change in the oxygen content in the samples and with the doping of vanadium dioxide with iron. It was established that vanadium dioxide VO2±X and solid solutions V1-XFeXO2 are paramagnetic both in the semiconductor and metallic states.

Hybrid magnetic materials based on polyethylene containing co and ni nanoparticles

New hybrid magnetic materials based on HDPE filled with Со and Ni nanoparticles have been prepared via the metal vapor synthesis. Properties of the metal-polymer composites have been elucidated as a function of MVS parameters and metal nature. The Faraday method has been applied to characterize the magnetic properties of the systems. The microstructure of the samples has been studied with a number of X-ray and synchrotron techniques, including XRD, EXAFS and SAXS. Core-level and valence band spectra were measured by XPS. The peak at binding energy of 282.8 eV characteristic of C-Ni bond was recorded in the C 1s spectrum. It was shown that properties of nanocomposite materials with similar compositions are determined both by the synthesis conditions and post-synthesis factors.

Some features of thermophysical properties of γ‐Gd2S3 ceramics based on real structure

AbstractThe heat capacity Cp, thermal diffusivity χT, and lattice thermal conductivity κlatt of ceramic solid solutions of sesquisulfides Gd3‐xVGd,xS4 (0 < x < 0.33) in the temperature range 300‐700 K has been studied. Changing the real structure, namely the concentrations of vacancies (NV) and deformation (NDc) centers of polycrystals, significantly decreases κlatt. A deviation of composition from the stoichiometry 2:3 is accompanied by an increase in the specific area of the crystallite boundaries per unit volume, and, hence, the concentration of deformation centers DC increases. This observation was confirmed by examining the short‐range order disturbance of the lattice and symmetry environment of the Gd3+ and S2− environment by Raman spectroscopy and the magnetic susceptibility Faraday method. Therefore the thermal diffusivity of gadolinium sesquisulfide is reduced because of the mean free path of phonons decrease. As a result, the thermal conductivity of the polycrystalline samples is reduced by 10%.

Complex research of vanadium dioxide in the homoginuity field

The complex research results of vanadium dioxide VÜ2±x obtained with X-ray analysis method, a method of vacuum adiabatic calorimeter and Faraday method are discussed. The samples temperature dependences of electrical resistivity, heat capacity, and also magnetic susceptibility are presented and they prove that these characteristics jump abruptly in the phase transition area. Thermophysical, electrical, magnetic properties of vanadium dioxide are established to vary with the oxygen content in the samples. Values of Debye characteristic temperatures θD for samples VO2±x determined at temperature 150 K are presented. Values of entropy change as an amount of electronic and phonon components at phase transition were calculated. The results obtained allow to consider the phase transition of a metal semiconductor as a Mott-Peierls transition, and also to use vanadium dioxide in temperature sensors manufacture.

Effect of synthesis conditions on the structure and properties of new SiC x N y M z materials for spintronics

To produce novel thin-film spintronic materials based on a thermodynamic simulation, condensed phases with a complex composition are deposited in Si–С–N–H–M systems (M = Fe, Co, Ni) in a wide temperature range of 500-1300 K. As a result of the simulation CVD diagrams of Fe–Si–C–N–H(He), Co–Si–C–N–H(He), and Ni–Si–C–N–H(He) systems are obtained which enable the optimization of the synthesis process for film materials such as SiC x N y Fe z , SiC x N y Co z , and SiC x N y Ni z . SiC x N y Fe z films are experimentally deposited from a gas mixture containing ferrocene (C5H5)2Fe, organosilicon compound 1,1,1,3,3,3-hexamethyldisilazane HNSi2(CH3)6 (HMDS) under reduced pressure in the temperature range 1073-1273 K. The dependence of the physicochemical and functional properties of SiC x N y Fe z films on the synthesis conditions is found by a comples of modern research techniques such as IR and Raman spectroscopy, EDS, XPS, SEM, HREM, and synchrotron radiation powder XRD (SR XRD). By the Faraday method and electron paramagnetic resonance (EPR) the magnetic properties of the films are analyzed. It is shown that at a synthesis temperature of 1123 K the films are paramagnetic, and at a higher deposition temperature of 1273 K they are ferromagnetic.

ON LIMITING THE VOLUME FRACTION OF PARTICLES IN THE DISPERSE SAMPLE (FOR THE TASkS ON CONTROLLING THEIR MAGNETIC PROPERTIES)

It was found that it is sufficient to have the values of magnetic susceptibility X of a disperse sample containing ferroparticles to obtain the values of magnetic susceptibility X ч of its particles (particularly, in solving many scientific applied tasks of magnetic control and/or magnetophoresis of such particles). It is important that the values of volume fraction (concentration) γ of the ferroparticles be low (feasible), when simple dependence is acceptable for determining X ч values: X ч = X/γ. The question of the criterion value of γ is considered (it is still a discussion question). This value is up to γ=0.02-0.05 (this is evaluated data existing for a long time) for magnetite samples and even up to γ=0.2-0.25 (circumstantial evidence - by determining the demagnetization factor of disperse ferromagnetic samples). Direct experiments based on the ponderomotive Faraday method are realized with the use of a powder sample within the range of volume fraction γ ≤ 0.3 (for disperse phase - magnetite). The results of the experiments show that the linear part of X(γ) relation ends at γ 0.2. This is confirmed by many other consolidate data obtained by using disperse samples of magnetite (powder, colloid). However, at lower values of γ (γ ≤ 0.02-0.05) “individual” linear relation between X and γ is found as the consolidate data show. Taking into account the proportionality coefficient this relation differs from the previous relation by about 18%. This means that it is appropriate to use X values obtained at γ ≤ 0.02-0.05 for obtaining more accurate values of X ч .

Definition of a magnetic susceptibility of conglomerates with magnetite particles. Particularities of defining single particle susceptibility

Data of a magnetic susceptibility of ferro-and the ferrimagnetic particles of many technogenic, natural, special media are especially demanded for the solution of various tasks connected with purposeful magnetic impact on these particles. One of productive approaches to definition of a magnetic susceptibility χ of these particles consists in receiving experimental data of a susceptibility of disperse samples 〈χ〉 with a disperse phase of these particles.The paper expounds and analyses the results of experiments on defining (by Faraday method in a magnetic field with intensity H=90–730kA/m) the magnetic susceptibility 〈χ〉 of disperse samples (conglomerates) with a given volume ratio γ of magnetite particles (γ=0.0065–0.25). The corresponding families of concentration and field dependences are provided alongside with discussing the applicability of linear and exponential functions to describe these dependences.We consider the possibility of defining single particles susceptibility χ (with simultaneous obtaining field dependence of this susceptibility) by the commonly used relation χ=〈χ〉/γ both at relatively small (preferable for accuracy reasons) values γ – to γ=0.02…0.025, as well as at increased values γ – up to γ=0.25.The data χ are provided depending on H and correlating with known data at H<90kA/m; they are obtained at small values γ when with almost double distance between the neighbouring particles (in comparison with their proper dimensions) the mutual adverse (to determine valid data χ)magnetic impact of particles is practically excluded. The article also gives the data χ received at increased values γ with almost halved distance between the surfaces of the neighbouring particles.It is specified that in the studied (post-extreme) area of H both variants of obtained field dependencesχare functionally identical within the accuracy of a constant, and close to an exponential dependence χ∼1/H0.75. With the account for the defined here value of constant-multiplier (0.8), it provides the grounds for obtaining valid data χ, employing the results of measuring 〈χ〉 for conglomerates with not obligatory small values of γ.It is demonstrated that being obtained by data χ, the calculated field dependence of the particle matter magnetic susceptibility χm (for the case when the particles are traditionally likened to balls with the characteristic for them demagnetising factor equalling 1/3) complies with the anticipated inverse function χm∼1/H in the studied area H (where magnetization M expressed as M=χH reaches saturation M=Const).

The working zone in the interpolar area of the Faraday balance: an approach to testing the magnetic force factor stability criterion

Due to rapid development of the scientific and applied research in magnetic control and magnetophoresis of ferro- and ferromagnetic disperse fraction of various technological, natural and industry-specific media, the Faraday method is again in high demand as it is mainly aimed at defining magnetic susceptibility of solid and heterogeneous samples of small volumes. Based on the appearing (and then measured) ponderomotive force impacting the sample, the method allows accurate determining of single particles magnetic susceptibility by using the data of the sample represented by a conglomerate of the particles of such a fraction. In addition, it is mentioned that to date there is still a great gap in the methodology of the Faraday method as there are no exact recommendations on choosing both the form of the polar pieces of the Faraday balance and the positioning of the sample (the location of the working zone) in the interpolar area. Owing to these drawbacks, the well-known and long-time used Faraday method cannot be considered substantiated to a satisfactory degree. Thus, in our point of view, the treatment of the results obtained earlier with the help of the method should be cautious. In our work, we experimentally defined and substantiated an approach to identifying a working (local) zone, viz. the zone with stable values of the magnetic force factor – the product of the field intensity and induction by its gradient. The approach features the relative phenomenological analysis and is exemplified by polar pieces of non-traditional spherical form. It has been demonstrated that in order to state the fact of mere existence of this zone (and its location) in the interpolar area, the coordinate (usually nonlinear one) characteristic of intensity or induction, which is obligatorily obtained in an experiment, should have an inflexion, which guarantees a functionally extreme view of the following coordinate characteristics both of the gradient and that of the force factor. We also established the coordinates and the length of the working zone in a specific interpolar area.

Magnetic behavior of Bi5Nb3–3xFe3xO15–δ solid solutions

Most bismuth compounds with layered perovskite-like structure, analogs of Aurivillius phases, exhibit ferroelectric properties and are of interest from both practical and theoretical points of view. In this study, we carried out magnetochemical measurements of an electronic state and exchange interactions between iron atoms in the solid solutions Bi5Nb3O15, obtained by heterovalent substitution of niobium by atoms of iron (III). The iron-containing solid solutions were obtained in a narrow concentration range at x≤0.06. The iron-containing solid solutions at concentrations x> 0.005 are characterized by monoclinic distortion of the tetragonal cell (P2/m). The measurements of magnetic susceptibility of the solid solutions were carried out by the Faraday method in the temperature range of 77 - 400 K. The isotherms of a paramagnetic component of magnetic susceptibility of iron atoms are typical of antiferromagnets. The effective magnetic moment of single iron atoms increases with increasing temperature from 6.87 mB (90 K) to 6.92 mB (320 K). The study of the iron-containing Bi5Nb3O15 solid solutions has shown that, in the solid solutions iron (III) atoms aggregate to form dimers and tetramers with antiferromagnetic and ferromagnetic types of exchange. The values of antiferromagnetic and ferromagnetic exchange in dimers, Jdim = - 60 cm-1 and Jdim = 40 cm-1, and tetramers, Jtetr = - 40 cm-1 and Jtetr = 25 cm-1 correspondently.

Magnetic Susceptibility of liquid Gd-NM (NM = Cu, Ga, Ge) alloys

For rare earth alloys, the indirect interaction of RKKY is at work between rare-earth atoms. Therefore, the magnetism of them depends on the number of conduction electrons and the distance between rare-earth metals. In this work, to reveal the relationship between the number of conduction electrons and magnetic property of rare earth metal alloys, magnetic susceptibility measurements for liquid Gd-NM (NM = Cu, Ga, Ge) was performed by Faraday method. As the results, it was observed that the sign of paramagnetic Curie temperature of Cu-Gd alloys are positive at all composition, while Ga-Gd and Ge-Gd alloys show negative paramagnetic Curie temperature at certain composition. Moreover, it was indicated when the alloy at certain composition shows highest melting temperature, it has the lowest paramagnetic Curie temperature.

Study the effect of Gd3+ incorporation into nanocrystalline (Ni–Ti) substituted Mn–Zn ferrites on its structure and functional properties

Ferrite samples with general chemical formula Mn0.9Zn0.1Ni0.05Ti0.05GdtFe1.9−tO4; (0.0≤ t≤0.05; step 0.01) were prepared using solid state reaction technique and the effect of Gd3+ ions incorporation on its physical properties has been studied. From the obtained results, XRD analysis reveals that the samples have a cubic spinel single phase structure for 0.0≤ t≤0.02; while for t≥0.03 a small peak of secondary phase (Gd3Fe5O12) appears and becomes more noticeable with increasing Gd content. The lattice parameter (a) of the prepared samples was found to be initially increases and then decreases with increasing Gd content which may be attributed to the difference in the ionic radii of the cations involved and the solubility limit of Gd3+ ions. The crystallite size of the samples was estimated using Scherrer's equation and ranged from 96nm to 107nm. A vibrating sample magnetometer (VSM) was used at room temperature in order to study the effect of Gd content on the magnetic hysteresis parameters of the prepared ferrites such as saturation magnetization and coercivity. DC molar magnetic susceptibility (χM) for the prepared samples was measured using Faraday's method as a function of temperature and the Curie temperature was calculated from the magnetic susceptibility measurements. Also the DC resistivity of the samples was measured at room temperature. The obtained results show that, the substitution by Gd3+ ions improves the electrical properties of the samples by increasing it DC electrical resistivity by 118% and consequently decreases it eddy current loss while the saturation magnetization slightly decreased by 14% only. The sample of t=0.01 shows a high dc magnetic susceptibility, high saturation magnetization (43.1emu/g), high electric resistivity 12×103Ω.m and high Curie temperature (496K), which is useful in some technological applications such as transformer and inductor cores.

Magnetic Properties of Rare-Earth Aluminoborates RAl3(BO3)4 (R = Th, Er, OR Ho) at High Temperatures

A temperature dependence of the magnetic susceptibility [χ(T)] of rare-earth borates RAl3(BO3)4 (R = Tb, Er, or Ho) is measured by the Faraday method at temperatures in the interval 20–850°С. Nonlinear anomalies caused by structural transitions are observed in the dependences χ–1(T). It is established that the dependences χ–1(T) for each phase obey the linear Curie–Weiss law. The Curie temperatures and the magnetic moments corresponding to the chemical formula of the compounds have been found.